Experimental diffusivity of energetic compounds determined by peak parking

Diffusivities of several explosive compounds, as well as other complex organic compounds were experimentally derived using a peak parking methodology. High performance liquid chromatography (HPLC) with stop flow ‘parking’ was used to experimentally determine diffusivity based on band broadening associated with chemical diffusion within the HPLC column. This research builds on prior methods by determining an obstruction factor through comparing benzene diffusion in methanol in a C18 column to the previously published capillary column. The method is useful for structures not easily described by computational chemistry methods or for solvents that do not have association coefficients in published diffusivity models. Using the peak parking method, diffusivities (cm2/s) ranged from 6.29 × 10-7 to 1.06 × 10-6 for hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), 4.82 × 10-5 to 1.26 × 10-4 for 3-nitro-1,2,4-triazol-5-one (NTO), 1.63 × 10-5 to 7.20 × 10-6 for nitroguanidine (NQ), 7.07 × 10-6 to 2.09 × 10-5 for pyrimidine-2-carboxylic acid, and 1.02 × 10-6 to 2.27 × 10-6 for streptomycin. Compared to diffusivities estimated computationally, the empirical diffusivities reported herein estimated by two different methods have percent differences averaging 142%, 174%, 27%, 85%, and 33% for RDX, NTO, NQ, pyrimidine-2-carboxylic acid, and streptomycin, respectively. NTO had experimental diffusivities greater than the computational values, while RDX and streptomycin had experimental diffusivities lower than computational values.